Research should shed light on oystercatcher migratory patterns

Published: Tuesday, July 2, 2013 at 10:49 a.m.

Last Modified: Tuesday, July 2, 2013 at 10:49 a.m.

It's a muggy morning on the south end of Wrightsville Beach, and Oreo the American oystercatcher is feeling territorial.

Facts

Appearance: Black heads and wings, with white feathers on chest and stomach. Bright red beaks and eyes.Feeding: Oysters, naturally, but also clams, mussels and other bivalves. The birds eat by inserting their sharp, skinny beaks into barely opened shellfish, turning them sideways and prying the halves apart.Habitat: Coastal locations from Maine to Texas, ranging from sandy North Carolina beaches to rocky shores in New England.Status: Federal species of interest, two steps below an endangered species. There are roughly 11,000 oystercatchers in the world.Online: Follow their movements and learn more at www.oystercatchertracking.org.

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Beachwalkers on their morning strolls keep veering too close to the patch of sand where Oreo's chick and mate are foraging. Each time a pedestrian steps too close, Oreo runs back and forth, peeping loudly every few seconds, a protective measure designed to distract predators while her baby scurries to hide in the nearby dune grasses.

Listening to the increased squawking as the beachwalker leaned over to peer at a washed-up jellyfish, Lindsay Addison nodded knowingly. "That's kind of the maximum distress call," said Addison, a coastal biologist with Audubon North Carolina,

Biologists and birders alike know plenty about the mannerisms, nesting habits and feeding preferences of the American oystercatcher, listed as a federal "species of interest," or two notches below an endangered species. But there's little information about the birds' migratory habits, a data gap that prevents experts from painting a complete picture of the seasonal routes the oystercatchers use and how long it takes them to complete those journeys. Up and down the North Carolina coast, Addison and other researchers aim to change that.

Since April, wildlife biologists from Audubon and N.C. State University have been trapping oystercatchers along the shore, outfitting them with small satellite tracking devices and then releasing them back into the wild.

Trapping methods rely heavily on the birds' territorial nature, Addison said. To snag and tag Oreo - named by students at Wrightsville Beach Elementary School as part of a lesson on shorebirds - biologists placed a decoy oystercatcher in the center of a knotted net, surrounded by wire mesh, then waited for her to pick a fight.

"Oreo became upset about the decoy and came to attack it, then stepped in the carpet," Addison said. "That prevents the birds from flying, and we can take and tag them with the trackers."

Similar to little backpacks, the trackers nestle on the birds' backs, attaching with flexible rubber straps. Each tagged bird has a green band around each leg and a long, flexible antenna sprouting from the middle of its back. Each satellite backpack costs about $3,000, purchased via a $45,000 grant from TogetherGreen that also helps defray other costs related to the project.

The devices - attached to a total of six birds from Ocracoke to Southport - communicate with satellites, pinpointing the oystercatchers' locations to within 250 meters. That data is downloaded by biologists each week and later plotted as point locations on tracking maps.

Each bird's path is drawn in a different color. Oreo's movements, represented by blue lines, spray out in a star pattern from Wrightsville Beach to nearby spoil islands in the Intracoastal Waterway. When the weather cools, those movements should stretch farther and farther, showing the exact route that Oreo takes to her winter habitat.

"We know the birds migrate, and some of the places they go," Addison said. "What we don't know is what kind of trip it is. Are they hopscotching down the coast, or is it a straight shot all the way to Florida?"

Deciphering those patterns will help identify the specific places the birds use on their journeys, allowing for more comprehensive conservation efforts. Not all oystercatchers migrate, but because the birds spend their entire life cycle on the coast, any information about their movements is helpful. Drilling the data down to specific birds could also have the fringe benefit of engaging non-birders, Addison said.

"The information helps identify the habitats the birds are using and what they need," Addison said. "We're trying to use the tracking to increase awareness and knowledge of coastal conservation, and of other birds who use the shore."